1. Field of the Invention
The present invention relates to a hot water supply apparatus including a high-pressure side heat exchanger connected to a refrigerant circuit and a hot water storage tank for storing hot water heated in the high-pressure side heat exchanger.
2. Description of the Related Art
Conventionally, there have been known hot water supply apparatuses of such type that include: a refrigerant circuit having an electric compressor, a high-pressure side heat exchanger, an expansion mechanism and a low-pressure side heat exchanger; a hot water storage tank for storing hot water; a circulation circuit having a supply pipe for connecting the hot water storage tank and a water inflow side of the high-pressure side heat exchanger, and a return pipe for connecting a water outflow side of the high-pressure side heat exchanger and the hot water storage tank; and a circulating pump provided in the circulation circuit.
In this hot water supply apparatus, generally, the circulation circuit is often laid outdoors, and water within the circulation circuit may freeze when operation of heating water to store hot water in the hot water storage tank is stopped at a low ambient temperature such as in the winter. Then, there is known a system adapted to perform operation of preventing freezing that prevents freezing in a manner that, when an ambient temperature becomes equal to or lower than a predetermined temperature, the circulating pump is operated to circulate water within the circulation circuit, and the compressor is operated to heat the water circulating within the circulation circuit.
However, in a conventional hot water supply apparatus, during operation of preventing freezing, the compressor is operated at the same rotation speed as that during operation of heating water, and the compressor is stopped when a temperature of water circulating within the circulation circuit becomes equal to or higher than a first predetermined temperature, and the compressor is operated when the temperature of water circulating within the circulation circuit becomes lower than a second predetermined temperature equal to or lower than the first predetermined temperature, so that the compressor is repeatedly operated and stopped, which presents a problem of increased power consumption.